This application is the national phase under 35 U.S.C. xc2xa7 371 of PCT International Application No. PCT/JP01/04036 which has an International filing date of May 15, 2001, which designated the United States of America.
The present invention relates to a method for producing a high purity alkyladamantyl ester by distilling and purifying a crude alkyladamantyl ester containing impurities.
Heretofore, when a solution to be distilled which contains a target compound also contains materials which promote decomposition of the target compound despite the fact that the target compound is a compound which is easily decomposed under influence of heat, a catalyst or the like, the target compound is easily decomposed during distillation. Therefore, it is difficult to obtain the target compound at a high purity or a high yield by purification by distillation. In general, even if a very small amount of materials which exhibit a decomposition promoting action is contained, it is very difficult to identify and remove the materials to such an amount that does not adversely affect the target compound because they cause decomposition of the target compound at the time of heating. In such a case, a purification method other than distillation must be used so as to purify a easily decomposable target compound with good reproducibility and at a high purity.
Meanwhile, demand for products of higher purity has been increasing every year. In particular, a reduction in metal components of a product used in a semiconductor production process is strongly demanded. As a purification method which can remove such metal components efficiently, purification by distillation is suitable.
In recent years, it has been reported that polymers obtained from alkyladamantyl esters having polymerizable groups have high dry etching resistance in a semiconductor production process (refer to JP-A 5-265212), and a possibility of their use as resist materials for semiconductors has been receiving attention. When these alkyladamantyl esters are used as resist materials for semiconductors, high purity alkyladamantyl esters having reduced metal components are required.
It is known that the alkyladamantyl ester can be produced by reacting 2-alkyl-2-adamantanol or 2-alkylideneadamantane which is obtained via 2-adamantanone from adamantane as a starting material or 2-adamantanone with an organometallic reagent such as methyl magnesium bromide so as to obtain a metal alkoxide and reacting a carboxylic acid derivative such as a carboxylic acid ester, a carboxylic anhydride or a carboxylic acid halide or a carboxylic acid with the obtained metal alkoxide.
In general, the alkyladamantyl ester is easily decomposed when stimulated by acid, heat or the like. For example, it is known that the alkyladamantyl ester is decomposed into a carboxylic acid or the like when heated in the presence of a catalytic amount of acid. By use of such a characteristic, the alkyladamantyl ester is used as a raw material for a chemically amplified resist in a semiconductor production process. Therefore, to purify the alkyladamantyl ester by distillation, it is commonly practiced to wash the alkyladamantyl ester with an alkali solution such as a sodium hydroxide solution as a pretreatment so as to remove acid components.
However, when a crude alkyladamantyl ester which has been subjected to a conventional pretreatment such as washing with an alkali solution so as to remove acid components is distilled by a commonly used method, the alkyladamantyl ester is decomposed during distillation for some reason, thereby producing a decomposition product such as a carboxylic acid or 2-alkylideneadamantane. Thus, a high purity alkyladamantyl ester has not been able to be obtained at a good yield.
Further, it has been found that a crude alkyladamantyl ester or a distilled and purified alkyladamantyl ester is decomposed during storage for some reason, thereby causing such a problem as coloration. In addition, it has also been found that an alkyladamantyl ester having a polymerizable group has a problem that when the alkyladamantyl ester is decomposed during storage to have coloration, a molecular weight does not increase even if it is polymerized.
An object of the present invention is to provide a method for producing a high purity alkyladamantyl ester by applying an efficient purification method to a crude alkyladamantyl ester for which an efficient distillation and purification method has not been known.
The present inventor has made intensive studies so as to solve the above problems. As a result, he has found that a crude alkyladamantyl ester can be purified efficiently by distilling the alkyladamantyl ester in the presence of a heterocyclic compound and/or a basic compound and that the above compounds also have an effect of improving storage stability of the alkyladamantyl ester. The present inventor has completed the present invention by these findings.
That is, the present invention is a method for producing a high purity alkyladamantyl ester which comprises the steps of esterifying an adamantane compound having an xe2x80x94OH group, xe2x80x94OM group or xe2x95x90R group (wherein M is an alkali metal atom or MgX (wherein X represents a halogen atom), and R is a divalent aliphatic hydrocarbon group) and distilling a crude alkyladamantyl ester obtained to form a high purity alkyladamantyl ester, wherein the distillation is carried out in the presence of a heterocyclic compound and/or a basic compound.
In the present invention, a crude alkyladamantyl ester to be distilled is obtained by esterification of an adamantane compound having an xe2x80x94OH group, xe2x80x94OM group or xe2x95x90R group (wherein M is an alkali metal atom or MgX (wherein X represents a halogen atom), and R is a divalent aliphatic hydrocarbon group). The crude alkyladamantyl ester obtained by such a process contains an impurity which can decompose the alkyladamantyl ester. Although the impurity has not heretofore been identified yet, the present inventors assume that it may be a compound which decomposes under distillation conditions and produces acid.
In the xe2x80x94OH group, xe2x80x94OM group or xe2x95x90R group (wherein M is an alkali metal atom or MgX (wherein X represents a halogen atom), and R is a divalent aliphatic hydrocarbon group) in the adamantane compound which is a raw material of the crude alkyladamantyl ester, the alkali metal atom represented by M is a potassium atom, a sodium atom or the like, and the halogen atom represented by X is a chlorine atom, a bromine atom, an iodine atom or the like. Further, the divalent aliphatic hydrocarbon group represented by R is exemplified by a divalent group having 1 to 4 carbon atoms such as a methylidene group, an ethylidene group, a propylidene group, an isopropylidene group and the like.
Illustrative examples of the adamantane compound having the xe2x80x94OH group, xe2x80x94OM group or xe2x95x90R group include 2-alkyl-2-adamantanol (wherein the alkyl group has 1 to 6 carbon atoms) having an xe2x80x94OH group, 2-alkylideneadamantane (wherein the alkylidene group has 1 to 4 carbon atoms) having an xe2x95x90R group, and a compound represented by the following formula (1) 
(wherein R1 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and M is an alkali metal atom or MgX (wherein X represents a halogen atom)).
Illustrative examples of a specific production method of the crude alkyladamantyl ester include a method comprising the steps of alkylating 2-adamantanone with a Grignard reagent such as an alkyl magnesium halide or an organometallic reagent such as alkyl lithium so as to obtain an adamantane compound having an xe2x80x94OM group and then esterifying the adamantane compound with a carboxylic acid halide; a method comprising the steps of alkylating 2-adamantanone with an organometallic reagent so as to obtain 2-alkyl-2-admantanol and then esterifying the compound with a carboxylic acid halide, carboxylic anhydride or carboxylic acid ester; and a method comprising the steps of alkylating 2-adamantanone with an organometallic reagent, dehydrating an alcohol obtained from decomposition of a metal alkoxide so as to obtain 2-alkylideneadamantane and then esterifying the compound with a carboxylic acid by means of an addition reaction.
The crude alkyladamantyl ester may contain impurities other than the aforementioned impurity which decomposes the alkyladamantyl ester as long as the impurities are those which can be separated by distillation. Illustrative examples of such impurities include adamantane and 2-adamantanone which are used as a raw material upon synthesis of the alkyladamantyl ester, 1-adamantanol which is an impurity derived from the raw material, 1-adamatyl ester and 2-alkylideneadamantane which are by-produced at the time of the synthesis, and tetrahydrofuran and hexane which are used as a solvent at the time of the synthesis.
The content of these other impurities is not particularly limited. When the crude alkyladamantyl ester is produced by any of the above methods, a total amount of the other impurities is about 1 to 50 parts by weight when the weight of the alkyladamantyl ester is 100 parts by weight.
As the alkyladamantyl ester to be purified in the present invention, a compound represented by the following formula (2): 
(wherein R2 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R3 is a hydrogen atom or a methyl group) is preferably used.
Illustrative examples of the alkyl group having 1 to 6 carbon atoms which is represented by R2 in the above formula (2) include linear alkyl groups such as a methyl group, ethyl group, propyl group, butyl group and hexyl group; and branched alkyl groups such as an isopropyl group, tertiary butyl group and neopentyl group. In particular, an alkyladamantyl ester represented by the above formula (2) in which R2 is a methyl group, ethyl group or butyl group and R3 is a hydrogen atom or methyl group is suitable since it is useful as a raw material for a resist for a semiconductor and a high degree of purification in particular is important.
In the present invention, the above crude alkyladamantyl ester is distilled in the presence of a heterocyclic compound and/or a basic compound (hereinafter also referred to as xe2x80x9cdecomposition inhibiting materialsxe2x80x9d).
In the present invention, as the heterocyclic compound which is one of the decomposition inhibiting materials, a compound having, in a molecule, at least one heterocyclic ring having at least one hetero atom selected from the group consisting of oxygen, nitrogen, sulfur, selenium and silicon and 2 to 6 carbon atoms as ring-member atoms is preferably used. The heterocyclic compound may have a plurality of hetero atoms in the same heterocyclic ring. Further, the heterocyclic compound may have a plurality of the same or different heterocyclic rings in a molecule independently, and may have heterocyclic rings as condensed rings of the heterocyclic rings or as condensed rings of the heterocyclic rings and aromatic hydrocarbon rings.
As the heterocyclic compound, a known heterocyclic compound may be used without limitation. For example, such a compound as one described in xe2x80x9cChemistry of Heterocyclic Compound, Third Revised Editionxe2x80x9d (published in 1980 by Kagaku Gijutsu Syuppansya) can be used.
As the heterocyclic ring contained in the heterocyclic compound in the present invention, a saturated three-to-five-membered ring is preferred. Illustrative examples of such a heterocyclic ring include cyclic ethers such as oxirane, oxetane and oxolane; cyclic thioethers such as thiirane, thiethane and thiolane; cyclic amines or N-alkyl substitution products thereof such as aziridine, N-methylaziridine and azetidine; cyclic siloxanes; and oxazines.
Of these, as a decomposition inhibiting material which exhibits a great effect of inhibiting decomposition of the alkyladamantyl ester and with which a higher purity target compound can be obtained, a heterocyclic compound having a cyclic ether structure in a molecule can be used. Above all, when a heterocyclic compound containing an oxirane ring or oxetane ring is used, it generally provides an effective decomposition inhibiting effect even in a small amount.
As the heterocyclic compound containing the cyclic ether structure, known compounds can be used without particular limitations. As the heterocyclic compound having the oxirane ring, compounds such as those described in a section in the 14th category (thermosetting resin) of xe2x80x9cChemical Commodity Product of 13599xe2x80x9d (published in 1999 by Kagaku Kougyo Nippou Sya), in a section of the second chapter (epoxy resin) of xe2x80x9cEpoxy Resin Handbookxe2x80x9d (published in 1987 by Nikkan Kougyo Shinbun Sya) and in a section of the third chapter (special epoxy resin) of xe2x80x9cNew Epoxy Resinxe2x80x9d (published in 1975 by Syokodo) can be used.
Illustrative examples of such compounds include oxirane compounds substituted by an alkyl group or an aryl group such as propylene oxide, 6,7-epoxydodecane, styrene oxide and xcex1,xcex1xe2x80x2-epoxydibenzyl; glycidyl ether compounds (including monomers and oligomers formed from two or more molecules) having a plurality of glycidyl groups such as phenyl glycidyl ether, glycerol diglycidyl ether, diglycidyl bisphenol A, brominated diglycidyl bisphenol A, diglycidyl bisphenol C, tetraglycidyl benzophenone, diglycidyl bisphenol F, triglycidyl-p-aminophenol, diglycidyl cyclohexane 1,3-dicarboxylate and novolac-type epoxy; glycidyl ester compounds such as diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, glycidyl dimer acid ester, diglycidyl hexahydrophthalate and diglycidyl-p-oxybenzoic acid; alicyclic epoxy compounds such as vinylcyclohexene dioxide and 7-oxabicyclo[4.1.0]hepta-3-ylmethyl-7-oxabicyclo[4.1.0]heptane-3-carboxylate; glycidyl amine compounds such as tetraglycidyl diaminodiphenylmethane, triglycidyl p-aminophenol and diglycidyl aniline; and heterocyclic epoxys having other heterocyclic structures together with an oxirane ring such as 1,3-diglycidyl hydantoin, glycidyl glycideoxyethyl hydantoin and triglycidyl isocyanurate.
Further, illustrative examples of the heterocyclic compound having the oxetane ring include 3-ethyl-3-hydroxymethyloxetane and 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene.
The basic compound which is the other decomposition inhibiting material is a compound which has an aqueous phase having a pH of larger than 7 when mixed with water (when not easily dissolved in water, a water-insoluble organic solvent such as hexane is further added thereto and shaken). Illustrative examples of such a basic compound include an oxide or hydroxide of an alkali metal or alkaline earth metal such as sodium hydroxide, potassium hydroxide, barium hydroxide, sodium oxide, magnesium oxide and calcium oxide; an inorganic weak base comprising a weak acid and a strong base such as potassium hydrogencarbonate, magnesium carbonate and sodium acetate; aluminum hydroxide and alumina; organic hydroxides such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide; aliphatic amines such as triethylamine, trioctylamine, ethanolamine, diethanolamine and triethanolamine; aromatic amines such as pyridine, dimethylaminopyridine, phenothiazine, dibutylphenothiazine, dioctylphenothiazine, N,Nxe2x80x2-diphenyl-p-phenylenediamine and N,Nxe2x80x2-dinaphthyl-p-phenylenediamine; inorganic complex compounds such as hydrotalcite, e.g., Mg6Al2(OH)16CO3.4H2O and zeolite, e.g., A-type zeolite; Lewis bases; and the like.
The above decomposition inhibiting materials are preferably those which do not react with the alkyladamantyl ester which is the target compound and do not decompose under distillation conditions. Further, to obtain a high purity alkyladamantyl ester, these decomposition inhibiting materials are preferably those which are not distilled out together with the target compound or can be easily separated from the target compound to be distilled out even if contained in the target compound.
In order not to be distilled out together with the target compound, the decomposition inhibiting materials preferably shows such a high boiling point that does not allow the decomposition inhibiting materials to be distilled out at the time of distillation, has neither a boiling point nor a sublimation point or shows such a low boiling point that does not allow the decomposition inhibiting materials to be distilled out together with the target compound. Particularly, to maintain the decomposition inhibiting effect until completion of the distillation of the target compound, the decomposition inhibiting materials are more preferably compounds which show such a high boiling point which does not allow the compounds to be distilled out at the time of the distillation or have neither a boiling point nor a sublimation point.
In a case where decomposition inhibiting materials which can be easily separated from the target compound are used, even when the target compound is distilled out and mixed with the decomposition inhibiting materials as the distillation proceeds, the target compound can be obtained at a high purity since the decomposition inhibiting materials can be removed easily. For example, if the target compound does not have compatibility with the decomposition inhibiting materials, the target compound can be obtained easily through liquid separation. Further, if water-soluble decomposition inhibiting materials are used when the target compound is insoluble in water, the target compound can be obtained easily by washing a distillate with water. Further, if water-insoluble decomposition inhibiting materials are used when the target compound is easily soluble in water, an acid solution or an alkali solution, the target compound can be obtained easily by dissolving a distillate in water, an acid solution or an alkali solution, removing the decomposition inhibiting materials by a liquid separating operation or the like, performing a neutralization operation as required, and removing water. In addition, when the target compound is insoluble in water and stable in acid or alkali, acid or alkali decomposition inhibiting materials can be used. In this case, the target compound can be obtained easily by washing a distillate with an alkali or acid solution.
The decomposition inhibiting materials are added in an amount sufficient to maintain the decomposition inhibiting effect and inhibit decomposition of the target compound. The amount of the decomposition inhibiting materials should be determined in consideration of an amount of decomposition promoting materials and is generally 0.0001 to 500 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the crude alkyladamantyl ester.
In the production method of the present invention, distillation of the crude alkyladamantyl ester is carried out in the presence of the decomposition inhibiting materials. A means for adding the decomposition inhibiting materials to the crude alkyladamantyl ester is not particularly limited. For example, the decomposition inhibiting materials may be mixed with the crude alkyladamantyl ester prior to initiation of the distillation or may be fed to a distiller directly or through a distillation column, distillation tube or reflux line after the initiation of the distillation. Further, as the decomposition inhibiting materials, a plurality of compounds can be used in combination.
In the production method of the present invention, a mode in which the distillation is carried out in the presence of the decomposition inhibiting materials is not particularly limited, and simple distillation or fractional distillation is used. In the case of the fractional distillation, as a fractionating column, a thin-film fractionating column such as a vigoureux-type fractional column, a concentric fractional column, a spinning band fractional column and a packed fractional column or a plate fractionating column such as a bubble-cap fractionating column and a porous plate-type fractionating column is suitably used. Particularly, when vacuum distillation is performed, a thin-film fractionating column which undergoes little pressure loss is suitably used. Further, a known distillation mode such as a Kugel roll or thin-film distillation can be used without any limitations.
In addition, distillation conditions including temperature, pressure and a reflux ratio are not particularly limited and may be determined as appropriate according to composition of the crude alkyladamantyl ester, types and amounts of the decomposition inhibiting materials, purity of the target compound to be obtained at the end, and the like. When the alkyladamantyl ester is the compound represented by the above formula (2), conditions including a temperature of 80 to 150xc2x0 C. and a pressure of 0.01 to 100 mmHg are preferably used.
As effects of the decomposition inhibiting materials, in addition to the above decomposition inhibiting effect, an effect of facilitating handling of the compound to be purified by decreasing the viscosity of the compound to be purified or forming the compound to be purified into a solution or suspension through addition of the decomposition inhibiting materials can also be expected, for example, even when the target compound is solid at room temperature. In a case where such an effect is expected, a liquid decomposition inhibiting material having a boiling point which is close to that of the target compound is suitably added, as a second decomposition inhibiting material, to the compound to be purified.
Further, in the present invention, the decomposition inhibiting materials also have an effect of improving storage stability of the alkyladamantyl ester. From the viewpoint of such an effect, as the decomposition inhibiting materials, a compound having an oxirane ring as a heterocyclic ring and an aromatic amine are particularly preferred among the aforementioned decomposition inhibiting materials.
In this case, the decomposition inhibiting materials are added in such an amount that can inhibit decomposition of a stored alkyladamantyl ester. The amount should be determined in consideration of efficacy of decomposition inhibiting materials to be used, solubility of the decomposition inhibiting materials against the alkyladamantyl ester and use of the alkyladamantyl ester. The amount is preferably 0.0001 to 100 parts by weight, more preferably 0.001 to 10 parts by weight, based on 100 parts by weight of the alkyladamantyl ester.
When it is not desirable that the decomposition inhibiting materials remain upon use of the target compound, decomposition inhibiting materials which can be easily separated from the target compound are preferably used so as to be able to remove the decomposition inhibiting materials easily by carrying out appropriate treatment before use of the target compound. As a method of separating the decomposition inhibiting materials from the target compound, methods which are the same as those mentioned above can be used.